Red ink thumbprints/fingerprints

Some sovereign citizens believe they must place a thumbprint or fingerprint next to their signature on a document for it to be valid. Most, though not all, who hold such beliefs further claim that the signature and fingerprint must be in red ink.

The origins of the sovereign citizen thumbprint idea date back to the late 1980s, though it only became popular in the 1990s. In some societies at some points in history, such prints were used as signatures or were required to accompany signatures.